Generally, in an image forming apparatus using a xerography such as a copier, a printer or a facsimile, in the image forming steps, a roller to which a conductivity is imparted such as a transfer roller, a developing roller, a toner supply roller, a charging roller, a cleaning roller, an intermediate transfer roller or a belt driving roller is used.
As the roller members used as developing rollers, charging rollers and transfer rollers (toner supply and cleaning) or the like, ones provided with a basic structure having an elastic layer comprising a conductive rubber, polymeric elastomer, polymeric foam or the like given electric conductivity by blending a conductive agent therein, which elastic layer is formed on the outer periphery of the shaft; and further with a single or multiple water-based coating layers on the outer periphery of the layer to attain a desired surface roughness, conductivity, hardness and the like; have been conventionally used.
However, there is a problem in that a surface layer using a water-based coating sticks to an image carrier due to having an excess amount of water when left under high temperature and high humidity, and thereafter, the layer is peeled off. For this reason, Patent Document 1 proposes a charging member in which the mass change of the material which forms the surface layer thereof due to water absorption accompanied by the environmental change from a temperature of 23° C. and a relative humidity of 50% to a temperature of 40° C. and a relative humidity of 95% is set to be 3.0% or less. Further, Patent Document 2 discloses a conductive member in which, for the purpose of obtaining a stable conductivity without being affected by the temperature or the humidity, a conductive fiber is planted on a substrate via an adhesion layer, and the conductive fiber has a structure in which a conductive polymer layer and a water-retaining layer are laminated.